The present invention relates generally to rotating electric machinery and, more particularly, to a method and system for protecting voltage regulator driver circuitry during a field coil short circuit condition.
Generators are found in virtually every motor vehicle manufactured today. These generators, also referred to as alternators, produce electricity necessary to power a vehicle's electrical accessories, as well as to charge a vehicle's battery. Generators must also provide the capability to produce electricity in sufficient quantities so to power a vehicle's electrical system in a manner that is compatible with the vehicle's electrical components. The alternator or generator typically uses a voltage regulator to regulate the charging voltage and output current in order to provide consistent operation during varying loads that would otherwise create voltage drops and other operational problems. Presently, conventional vehicle charging systems may utilize a voltage regulator having either a discrete transistor or, alternatively, a custom integrated circuit known as an Application Specific Integrated Circuit (ASIC).
Still other vehicle designs may also employ voltage regulators with advanced microprocessor functions that maintain a highly accurate regulated voltage produced by a generator. Microprocessor based regulators may also include advanced clock and memory circuits that store battery and power supply reference data, battery voltage and generator rotation speed, as well determine how much the battery is being charged and at what rate at any point in time.
In operation of a vehicle alternator, it is possible that the field coil used to generate the magnetic field of the rotor portion of the alternator may become short-circuited. In such a case, the voltage regulator driver circuitry should be deactivated in order to discontinue the flow of field current through the driver devices until such time as the short circuit condition is cleared. Conventionally, such short circuit protection (when provided at all) involves use of a number of components, such as (for example) a small shunt resistance within the field coil path and an analog voltage comparator to determine whether the voltage across the shunt resistor exceeds a nominal voltage when the field coil is not short circuited. Accordingly, it would be desirable to be able to provide short circuit protection for voltage regulator driver circuitry in a manner that results in fewer hardware components and/or reduced component costs.